A place of business in the United States is any location in the United States, its territories, or its possessions where a firm’s employees or agents regularly have personal contact with other individuals for conducting the firm’s business. For the purposes of this section, a firm whose employees or agents have personal contact with others for conducting the firm’s business in different places in the United States for short periods (for example, at hotels in different cities for 1 or 2 days at a time) is considered to have a place of business in the United States if the aggregate amount of time spent in the United States is 180 days or more within 12 consecutive months.